1. Field of the Invention
The present invention is directed to the field of volumetric flow measurement and more specifically to the area of overcoming errors inherent in flow sensor devices.
2. Description of the Prior Art
Many devices have been disclosed in the prior art that are alleged to accurately monitor liquid flow in a tube or pipe.
Turbine devices, such as those disclosed in U.S. Pat. Nos. 3,135,116; 3,867,840; and 4,011,757; each utilize rotating blades of a turbine to interrupt a light path from a source to a detector so that pulses are produced which are directly related to the speed of the rotating turbine and correspond to the flow of liquid through the device.
Other types of flow sensors, such as those disclosed in U.S. Pat. Nos. 4,012,949; 4,212,195; and 4,212,200, utilize dynamic force of the flowing liquid to effect electrical changes that may be measured to determine flow rates.
Still other types of fluid flow sensors, such as those disclosed in U.S. Pat. Nos. 2,776,568 and 4,050,295 utilize rotating balls in a closed flow track that are individually forced past a sensing element to represent a unit of flowing liquid.
While each of the fluid flow sensors of the prior art have distinct advantages and disadvantages with respect to each other, they each have a common disadvantage in that when located in various climatic regions where environmental temperatures are comparatively extreme, errors exist between devices of a like kind. It has been found that large errors in the number of pulses per unit of flowing liquid is not uncommon in existing flow sensors when subjected to extreme temperatures in flowing fluids. Similarly, errors in output develop as flow sensors age.
When such units are employed in liquid consumption measuring systems that utilize electrical components with comparatively low error tolerances, the potential for flow sensor errors exists for the output information to be inaccurate and unreliable.